[PATCH AUTOSEL 6.13 19/21] alpha/elf: Fix misc/setarch test of util-linux by removing 32bit support

Sasha Levin
2025-02-11T01:30:42Z

From: "Eric W. Biederman" <ebiederm@xmission.com>

[ Upstream commit b029628be267cba3c7684ec684749fe3e4372398 ]

Richard Henderson <richard.henderson@linaro.org> writes[1]:

> There was a Spec benchmark (I forget which) which was memory bound and ran
> twice as fast with 32-bit pointers.
>
> I copied the idea from DEC to the ELF abi, but never did all the other work
> to allow the toolchain to take advantage.
>
> Amusingly, a later Spec changed the benchmark data sets to not fit into a
> 32-bit address space, specifically because of this.
>
> I expect one could delete the ELF bit and personality and no one would
> notice. Not even the 10 remaining Alpha users.

In [2] it was pointed out that parts of setarch weren't working
properly on alpha because it has it's own SET_PERSONALITY
implementation. In the discussion that followed Richard Henderson
pointed out that the 32bit pointer support for alpha was never
completed.

Fix this by removing alpha's 32bit pointer support.

As a bit of paranoia refuse to execute any alpha binaries that have
the EF_ALPHA_32BIT flag set. Just in case someone somewhere has
binaries that try to use alpha's 32bit pointer support.

Link: https://lkml.kernel.org/r/CAFXwXrkgu=4Qn-v1PjnOR4SG0oUb9LSa0g6QXpBq4ttm52pJOQ@mail.gmail.com [1]
Link: https://lkml.kernel.org/r/20250103140148.370368-1-glaubitz@physik.fu-berlin.de [2]
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Tested-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Link: https://lore.kernel.org/r/87y0zfs26i.fsf_-_@email.froward.int.ebiederm.org
Signed-off-by: Kees Cook <kees@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/alpha/include/asm/elf.h | 6 +-----
arch/alpha/include/asm/pgtable.h | 2 +-
arch/alpha/include/asm/processor.h | 8 ++------
arch/alpha/kernel/osf_sys.c | 11 ++---------
4 files changed, 6 insertions(+), 21 deletions(-)

diff --git a/arch/alpha/include/asm/elf.h b/arch/alpha/include/asm/elf.h
index 4d7c46f50382e..50c82187e60ec 100644
--- a/arch/alpha/include/asm/elf.h
+++ b/arch/alpha/include/asm/elf.h
@@ -74,7 +74,7 @@ typedef elf_fpreg_t elf_fpregset_t[ELF_NFPREG];
/*
* This is used to ensure we don't load something for the wrong architecture.
*/
-#define elf_check_arch(x) ((x)->e_machine == EM_ALPHA)
+#define elf_check_arch(x) (((x)->e_machine == EM_ALPHA) && !((x)->e_flags & EF_ALPHA_32BIT))

/*
* These are used to set parameters in the core dumps.
@@ -137,10 +137,6 @@ extern int dump_elf_task(elf_greg_t *dest, struct task_struct *task);
: amask (AMASK_CIX) ? "ev6" : "ev67"); \
})

-#define SET_PERSONALITY(EX) \
- set_personality(((EX).e_flags & EF_ALPHA_32BIT) \
- ? PER_LINUX_32BIT : PER_LINUX)
-
extern int alpha_l1i_cacheshape;
extern int alpha_l1d_cacheshape;
extern int alpha_l2_cacheshape;
diff --git a/arch/alpha/include/asm/pgtable.h b/arch/alpha/include/asm/pgtable.h
index 635f0a5f5bbde..02e8817a89212 100644
--- a/arch/alpha/include/asm/pgtable.h
+++ b/arch/alpha/include/asm/pgtable.h
@@ -360,7 +360,7 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)

extern void paging_init(void);

-/* We have our own get_unmapped_area to cope with ADDR_LIMIT_32BIT. */
+/* We have our own get_unmapped_area */
#define HAVE_ARCH_UNMAPPED_AREA

#endif /* _ALPHA_PGTABLE_H */
diff --git a/arch/alpha/include/asm/processor.h b/arch/alpha/include/asm/processor.h
index 55bb1c09fd39d..5dce5518a2111 100644
--- a/arch/alpha/include/asm/processor.h
+++ b/arch/alpha/include/asm/processor.h
@@ -8,23 +8,19 @@
#ifndef __ASM_ALPHA_PROCESSOR_H
#define __ASM_ALPHA_PROCESSOR_H

-#include <linux/personality.h> /* for ADDR_LIMIT_32BIT */
-
/*
* We have a 42-bit user address space: 4TB user VM...
*/
#define TASK_SIZE (0x40000000000UL)

-#define STACK_TOP \
- (current->personality & ADDR_LIMIT_32BIT ? 0x80000000 : 0x00120000000UL)
+#define STACK_TOP (0x00120000000UL)

#define STACK_TOP_MAX 0x00120000000UL

/* This decides where the kernel will search for a free chunk of vm
* space during mmap's.
*/
-#define TASK_UNMAPPED_BASE \
- ((current->personality & ADDR_LIMIT_32BIT) ? 0x40000000 : TASK_SIZE / 2)
+#define TASK_UNMAPPED_BASE (TASK_SIZE / 2)

/* This is dead. Everything has been moved to thread_info. */
struct thread_struct { };
diff --git a/arch/alpha/kernel/osf_sys.c b/arch/alpha/kernel/osf_sys.c
index 86185021f75ae..a08e8edef1a44 100644
--- a/arch/alpha/kernel/osf_sys.c
+++ b/arch/alpha/kernel/osf_sys.c
@@ -1210,8 +1210,7 @@ SYSCALL_DEFINE1(old_adjtimex, struct timex32 __user *, txc_p)
return ret;
}

-/* Get an address range which is currently unmapped. Similar to the
- generic version except that we know how to honor ADDR_LIMIT_32BIT. */
+/* Get an address range which is currently unmapped. */

static unsigned long
arch_get_unmapped_area_1(unsigned long addr, unsigned long len,
@@ -1230,13 +1229,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
unsigned long len, unsigned long pgoff,
unsigned long flags, vm_flags_t vm_flags)
{
- unsigned long limit;
-
- /* "32 bit" actually means 31 bit, since pointers sign extend. */
- if (current->personality & ADDR_LIMIT_32BIT)
- limit = 0x80000000;
- else
- limit = TASK_SIZE;
+ unsigned long limit = TASK_SIZE;

if (len > limit)
return -ENOMEM;
--
2.39.5